Plaster and process of making the same



Patented May 29, 1923.

UNITED STATES PATENTOFFICE.

PIERRE E. HAYNES, OF BUFFALO, AND GEORGE P. GERFIN, O15 NIAGARA FALLS,NEW

YORK, ASSIGNOBS TO THE LINDE AIR N0 Drawing. Application filed April 29,

To all whom 1' t m (by concern Be it known that we, Tnzinuc E. l-hrnnsand GEORGEP. G'nnriN. citizens of the United States, residing at Buffaloand Niagara Falls, respectively, in the counties of Erie and Niagara andState of New York, have invented certain new and useful Im rovements inPlaster and Processes of h aking the Same, of which the following is aspecification.

Our invention relates to compositions suitable for making plaster-boardand for other purposes for which plaster is employed, and to processesfor making such compositions. More specifically, our invention relatesto the production of plaster from lime sludges which are by-products ofcertain industries. The object of our invention is to produce a plasterhaving valuable properties, and to utilize lay-products which are now inmany cases worse than worthless since their disposal involves largeexpense.

As an example of the sludges referred to above, the residue left on thedecomposition of calcium carbide to produce acetylene may be mentioned.It is well-known that this residue consists chiefly of slaked lime(Ca(OH) and water, but the quantity of water present is usually so highthat the cost of dehydrating the sludge for the recovery of its limewould be prohibitive. In the standard procedure for producing acetylenefrom calcium carbide on the large scale, the residue containsapproximately 88% of water.

As an example of the manner in which our invention is practised, aprocess which gives good results will be described: Sludge of thecomposition indicated above is treated for the removal of a portion ofits water in an apparatus such as a Dorr or Genter thickener, where itis concentrated until it contains 40-50% of solid matter. The thickenedsludge is then mixed in any suitable apparatus with a pnlverulentwater-absorbing material having cementitious properties supplementingthose of the lime. Ground coal ashes are well suited for this purposebut ground slag from metallurgical operations also give good results.lVithin rather wide limits in the proportion of water-absorbent tothickened sludge, a plaster is formed of suitable consistency and havingdesirable qualities on setting. Very good results have rnonucrs COMPANY,a CORPORATION or or MAKING THE SAME.

1921. Serial No. 465,480.

been obtained where the ratio of thickened sludge to ground ashes variedfrom 1:1 to .1: :1. It a sludge oi low water content is available,thickening may be dispensed with.

In some cases. it is desirable to add to the plaster small amounts atother substances to modify its properties. For example, up to 5% ofasbestos may be added and other fibrous materials may likewise be used.Silicate of soda in suitable quantity, for exam pie 3%, increases thestrength of the plaster after setting and may also be added to themixture. In general, however, the final product is cheapest and bestwhen the quantity of materials other than sludge and pulrerulentwater-absorbent is kept low.

lVhile plaster formed in the above manner is suitable for all uses towhich plaster is applied, it is especially adapted to the manufacture ofplaster-board. Processes for making such board and machines for thepurpose are widely known and used and our plaster may be substituted forthe gypsum plaster now generally employed with little or no change inprocedure except the allow ance of a considerable period for the plasterto take its initial set. Excellent results have been obtained with ourplaster by air-drying the freshly-formed board for 18 to 20 hours andthen drying with tree circulation of air for 241- to 30 hours at about100 C. The board is then preferably stored for about ten days forseasoning before it is shipped.

lVe claim:

1. The process of treating lime sludge containing lime as the principalnon-aqueous ingredient which comprises mixing it with a water-absorbingcementitious material in such proportions that a mixture of plasterlikeconsistency is formed.

2. The process of treating lime sludge con taining lime as the principalnon-aqueous ingredient which comprises mixing it with coal ashes in suchproportions that a mix ture of plaster-like consistency is formed.

3. The process of treating lime sludge which comprises thickening thesludge, mixing it with a waterabsorbing cementitious material, andregulating the degree of thickening and the quantity of water-absorbingmaterial used so that a mixture of plasterlike consistency is formed.

4. The process of treating lime sludge which comprises thickening thesludge, mixing ;it with coal ashes and iregiilating the degree ofthickening and the quantity of ashes used so that a mixture ofplaster-like consistency is formed.

5 ill-composition of plaster-like consistency comprising a pulverulentWater-absorbing cementitious material and lime sludge containing lime asthe principal nonaqueous ingredient.

. Aicomposition of plaster-like consistency comprising coal ashes and atleast an equal Weight of lime sludge.

7. A hardened sensibly dry plaster such as may be formed by the set-tingof a mixture consistingessentially of gronndveoal ashes and atlenst aneq'nrilkweight of lime sludge.

In testimony whereof, We ailix .our signatures.

GEORGE P. HEREIN. PIERRE E. HAYNES.

